On Saturday morning (2013 Oct 19) a bit of the Earth's shadow falls onto the Moon. The diagram above & right shows the Earth's shadow, and the changing position of the Moon. Luna only moves into the outer, fuzzy region of the shadow (penumbra) and doesn't make it into the darker inner shadow (umbra), so the effect will be a very slight darkening of the Moon. This effect is so gentle that it won't be noticeable unless you're looking for it.

The three small diagrams below it show the view from the Moon looking back at the Earth - this is an African eclipse.

To spot the shadow, look for a darkening that will first be visible in the area of the lovely crater Tycho (upper-right side of the Moon, so to speak). The eclipse starts on Friday night, at 23:48, but unless you're Superman you won't notice anything. The Moon is deepest inside the shadow at 01:50 on Saturday morning, when about 80% of it is eclipsed. At 03:51 the Moon exits the penumbra.

Be advised it is, of course, Full Moon (31.9' diameter) on Saturday, so beware of vampires and werewolves.